Much benefit could be realized by delivering therapeutic fluids to the direct vicinity of the surgical wound. Reduced pain, enhanced wound healing, and reduced occurrence of surgical site infections are but a few potential benefits. However, the form and function of a device that could cost-effectively facilitate localized delivery of therapeutic fluids directly to the wound site over an extended period of time are not apparent. Intravenous (IV) delivery of medication to the patient following a surgical procedure is common practice. The physician may use an IV to deliver a wide variety of medications directly to the patient's blood stream over an extended period of time. Intravenous (IV) administration of medication is indeed a systemic method of drug delivery where the medication will circulate through the entire body before a portion of the medication is delivered to the wound site. Since much of the medication may be metabolized at other locations within the body before reaching the wound site, it is often necessary to increase the overall amount or concentration of medication to be delivered systemically with an IV in order for an efficacious amount to reach the wound site. However, in many cases, the increased concentration of medication that may provide the most efficacious result at the wound site, may not be safely delivered through an IV since toxic side effects may occur at various organs within the body. Other medications, such as certain local anesthetics, only provide an efficacious result when delivered locally and are simply not compatible with IV delivery methods.
Multiple injections in and around the surgical wound, before, during and after surgical procedures have been used in an effort to deter side effects and complications associated with surgical procedures. Although the syringe and hypodermic needle provide a means for localized drug delivery, the continuous delivery of medication via injection over an extended time period is not practical. Indeed, over time the medication dissipates to a concentration below that required to achieve a therapeutic effect and additional injections must be prescribed. Moreover, in the case where the surgical wound is the local target for drug treatment, multiple injections around the wound site may be required to achieve the desired therapeutic effect. The patient may suffer discomfort and repetitive disturbance if multiple injections must be repeatedly administered. As a further draw back, with this approach, the health care professional must dedicate their valuable time and attention to repeatedly apply localized injections.
In order to address the aforementioned shortcomings of the IV and injections for the localized and continuous delivery of therapeutic fluids, a number of specialized infusion catheters for use in the wound site have been developed. These specialized infusion catheters typically exhibit multiple perforations along their lengths and are connected to a reservoir and pump that contain and feed the therapeutic liquid to the infusion catheter, for example as described in U.S. Pat. Nos. 5,458,582, 5,891,101 and 6,626,885. The infusion catheter itself may be placed directly into the surgical incision and held in place by closing the wound around it. However, a greater risk of infection and compromised wound healing may be associated with this deployment method since the infusion catheter may serve as a pathway for pathogens to enter the surgical incision. More commonly, the infusion catheter is passed through the skin and subcutaneous tissue in the vicinity of the wound, leaving the tip of the catheter within the surgical incision and the body of the catheter in healthy tissue surrounding the wound. It is important to note that the implantation of an infusion catheter in this manner commonly requires the use of a cannula to puncture and guide the infusion catheter though the skin and subcutaneous tissue and into the surgical incision site. Although these catheters provide a means of continuously delivering a therapeutic fluid to the wound, a number of drawbacks exists. Many devices such as described in U.S. Pat. No. 6,626,885 require the use of cannulas and additional puncture wounds in the vicinity of the surgical wound to firmly secure the catheter in place, while others described in U.S. Pat. Nos. 5,891,101 and 5,458,582 require the use of additional sutures or a modification of the suturing procedure. Even so, the infusion catheter may not be firmly anchored and accidental removal of the catheter from the wound site by the patient is not uncommon. Alternatively, in order to reduce patient discomfort and other complications associated with catheter removal, some catheter devices such as described in U.S. Pat. No. 5,458,582 may be produced from bioabsorbable materials. However, the implantation of bioabsorbable catheters increases the amount of material that must be absorbed and metabolized by the body, and it is generally desirable to keep this bioburden to a minimum. Finally, there are significant additional costs, ranging from hundreds to thousands of dollars, associated with the use of these specialized catheters and the supporting reservoirs and pumps that must be employed for their operation.
A suture that could be used for localized and continuous drug delivery could satisfy the unmet needs of the aforementioned devices. The suture is implanted into the tissue surrounding the wound, which is indeed the region that may benefit most from localized drug delivery. Further, since the suture must be present in most cases to achieve wound closure, the number of invasive procedures that a patient must suffer is not necessarily increased. Moreover, suture needles attached to one end of the suture may be used to penetrate tissue surrounding the wound and facilitate placement of the fluid infusing suture. The suture may be secured in the wound by making a knot in one end to prevent accidental removal. Moreover the flexibility exhibited by a suture is considerable greater than the flexibility exhibited by infusion catheters, consequently, the suture may be placed in a complicated pattern or in locations that would be hard to reach with a conventional infusion catheter. Although a number of benefits may be achieved if drug delivery from a suture were possible, the form and function of such a device is not apparent.
The concept of hollow monofilament sutures was first disclosed in U.S. Pat. No. 3,918,455. Although this patent focused on the use of hollow sutures to facilitate attachment to the suture needle, it was also suggested that the bore of the hollow suture could be filled with a fluid at the time of its installation to expedite dissolution of the suture material or render the suture visible by X-radiography. It was further suggested that the tube could be so extruded and drawn to be converted into a microporous state. In this state, the polymer comprising the wall of the hollow suture would permit fluid contained in the bore of the suture to gradually diffuse through the wall into the surrounding tissue. In U.S. Pat. No. 5,984,933 an apparatus for suturing tissue has been described. Although the patent focuses on a method and device to facilitate endoscopic suturing, it was suggested that the suture material of the device could be solid or hollow, and when the suture material is hollow, small holes in the wall of the suture can be formed to enable medicaments contained in the bore of the suture to leach out into the surrounding tissue. Although these patents suggest that hollow sutures may be used to contain, and in some embodiments even slowly emit a therapeutic fluid, there are some critical shortcomings that remain unaddressed. First of all, monofilament sutures are flaw sensitive. The introduction of pores or perforations into the wall of the hollow suture may result in a substantial decrease in the strength performance of the suture and lead to its inability to insure secure closure of the wound. Secondly, the amount of medicine that may be contained inside of a hollow suture is small. Indeed the maximum amount of drug bearing solution that may be contained within most hollow sutures is on the order of 0.005 ml or less, whereas many commercially available drug bearing solutions are efficacious only in quantities in excess of 1 ml. For example, anesthetic agents such as marcaine, lidocaine, bupivacaine, mepivacaine and procaine are typically injected into the tissue surrounding an incision or wound in a buffer solution at an overall volume ranging from 5 to 30 ml, which is 500 to 3000 times greater than the dose that is applicable with the hollow sutures disclosed in U.S. Pat. Nos. 3,918,455 and 5,984,933. Finally, once the hollow suture is implanted into the tissue surrounding the wound, the drug delivery rate is dictated by the rate at which the fluid leaches or diffuses through the multiple perforations or pores. Active control of the drug delivery rate and continuous drug delivery are not possible. Furthermore, if an adverse reaction to the drug occurs, the suture must be excised from the wound to terminate drug delivery.
U.S. Pat. No. 4,159,720 describes a means for infusing liquids into tissue. The preferred embodiment comprises a reservoir for containing fluids attached outside the body that feeds liquid to an absorbent wick. The absorbent wick may be made from materials commonly used in the manufacture of sutures and may be installed in the tissue in a variety of ways including placement inside of the incision or deployment in the tissue surrounding the wound. The invention relies on capillary action to draw fluid in and control the delivery rate. As such, fluid delivery rate may not be increased or decreased at the physician's discretion. Moreover, the rate of fluid influx will depend on the type of wicking material used and the thickness and length of the wick installed. It is also important to note that in the cases when the suture is comprised of a material or is coated with a material that is not wetted by the fluid, wicking action will not occur and the device will not function. Even when the fluid to be delivered does indeed wet the wick, one may expect the fluid delivery rate driven by capillary forces that may be evolved within a suture to be several orders or magnitude slower than fluid delivery rates achievable by other means such as IV, infusion catheter, or injection.
It may be desirable to have of a suture that serves the multiple functions of wound closure and drug delivery. However, unlike the aforementioned examples of prior art, the suture should: 1) not compromise critical performance characteristics such as strength of the suture, 2) enable delivery of an efficacious volume of drug bearing solution on the order of milliliters not microliters, 3) provide a high level of drug delivery rate control and enable the physician to start or stop drug administration at his/her discretion, 4) provide a means of providing more than one type of medication that may be selected post-surgically in accord with unexpected patient symptoms that may arise, 5) function regardless of the composition and wetting characteristics of the suture material.
A suture that satisfies the aforementioned criteria for wound closure and drug delivery is disclosed herein. It is important to note that while the device disclosed herein may be used in a multifunctional manner to close wounds and infuse fluids to a wound site, simpler applications where the suture acts solely as an infusing device are likewise possible and useful. Components of the suture may include a connector designed to join a fluid reservoir, such as an IV, or syringe, or infusion pump to a braided suture that contains at least one internal passageway capable of conducting a fluid along at least a portion of its length. The therapeutic fluid passes from the reservoir, through the connector, into the internal passageway and into the interstices between the multiple filaments of the braided suture. The integrity of the braided suture is not compromised in the design of this device and critical performance characteristic such as suture strength are maintained above United States Pharmacopia, USP, standards. By employing a connector to link the fluid conducting element of the suture to an external reservoir, the amount of therapeutic fluid that may be delivered through the suture may be increased to a volume that is efficacious. Moreover, by regulating the supply of therapeutic fluid, the drug delivery rate may be actively controlled and more than one type of medication may be supplied as needed.